Renewable energy sources have developed rapidly in recent years. In particular, isolated direct current (DC) microgrids have emerged as new grid structures for the comprehensive utilization of renewable energy and have good development prospects in industrial fields. However, the stability analysis of isolated DC microgrids still faces a significant challenge owing to the strong coupling of power converters and abundant transient processes. Thus, a new stability analysis framework for isolated DC microgrids is provided. In detail, the multi-timescale characteristics and stability issues of isolated DC microgrids are first analyzed, and three timescales are defined: the switching period timescale, device control timescale, and system control timescale. Subsequently, the existing stability indices of the microgrids are introduced, and a stability analysis framework for isolated DC microgrids is proposed based on the three defined timescales in this study. Finally, future research directions for the stability of isolated DC microgrids are discussed, and conclusions are drawn. The proposed stability analysis framework provides a reference for solving the stability problems in isolated DC microgrids, such as wide-frequency-band oscillations and the offset of the AC frequency.

Current topology recommendation methods for DC-DC converters predominantly rely on manual experience, often involving the analysis of performance metrics (either manually or via a computer) and subsequently selecting the most suitable topology to meet specific engineering requirements. However, as the number of available topologies increases and engineering demands vary, these methods are increasingly unable to provide optimal recommendations. To address this limitation, the present study presents an automatic optimization topology recommendation method (AO-TRM) for DC-DC converters that can accommodate a broad range of engineering requirements. The proposed method begins by identifying precise engineering requirements and then progresses through three key stages: topology generation, analysis, and recommendation. Two engineering applications are used as case studies to validate the effectiveness and capabilities of the proposed AO-TRM. From a pool of 1186 topologies, the proposed method successfully identified and recommended optimal topologies based on specific requirements. Finally, experimental results are presented, demonstrating the capability, efficiency, and cost-effectiveness of the proposed method.

Applications for near-space aerostats are numerous and include scientific experiments, geological exploration, and communication support. The power conversion equipment in these systems must have characteristics like high efficiency, miniaturization, and lightweight construction because of their particular operating environment. The significance of creating a DC-DC converter with high efficiency, high power density, and high voltage gain is highlighted by the low output voltage of the solar cell in the aerostat power system and the high voltage of the DC bus. Thus, using a high gain clamping capacitor converter and non-resonant soft-switching approaches, this work suggests a novel non-resonant linear (NRL) soft-switching DC-DC step-up converter with current balancing. The suggested converter can eliminate the device current spike brought on by charging and discharging capacitors by implementing zero-current-switching (ZCS) turn-on of switches and ZCS turn-off of diodes. Finally, the validity and correctness of the proposed converter are verified by simulation and experiment, which provides a novel topology choice for DC-DC step-up converter in near-space aerostat power systems.